Carb Help? Quadrojet
 

My 1989 Stingray 260Merc/Alpha 23p prop falls on it face when the secondary starts to open @3500-3800 and it will not recover until I throttle back. I conditioned the gas and filled the tank with 93 and still same situation. Should I change the water seperator, check timing, carb kit, is there any other filters in the line besides the seperator? How do you check the timing, is there a wire you have to disconnect to stop the advance? I am at a loss, just purchased the boat and made a move from old jets to merc and things are different. I could really use some help. This Stingray is fast without the secondary and I cannot wait to get them to open.

I'm assuming you've already replaced the water separating filter and checked the fuel screen behind the 1" fuel inlet fitting on the carb, and that you've run a fuel pump volume test. There are a couple very easy things to look at on the carb before digging in with a carb kit. Check the tension on the secondary air door, which is the big spring-loaded plate on top of the back venturii. I've seen the air door jammed in the open position which can cause the condition you describe. You should be able to open the air door without much pressure but it shouldn't just flop open either. Also, while you are checking the air door, you may notice two metering rods hanging from a bracket right behind the flame arrestor stud. These rods rise as the air door is opened. Make sure this linkage is working properly and if you need to, remove the little straight-slot screw from the bracket and carefully lift the bracket/metering rods up and out of the carb to see if a rod is bent. Be careful not to drop any parts into the primaries. This would be a bad thing. If the rods appear to be ok, re-install them by carefully lowering the rods/bracket back into position. Hope this helps. Dave

Definitely change the fuel filter/seperator and check the filter in the carb inlet. You'll need a 9/16 line wrench and a 1" wrench to get at the carb filter. I pulled mine out this past weekend (350MAG w/Q-Jet) and it was partialy clogged.
Check the timing too while you're at it, as well as the cap and rotor.
Sounds like carb trouble though. The secondaries are vacum operated and when they open, if there's no fuel, it'll just die.
Carb kit is good idea just make sure it's for a marine card and not automotive. If you don't feel like doing it yourself contact JET Performance they specialize in Q-Jet carbs and they quoted me a price to do mine for about $200.00.
If you do it yourself pick up several cans of spray carb cleaner along with the carb dip solution. Use the spray after the dip to blast out all the passages. Makes a difference.
Good luck.

Timing??? Advance disabling?
 

Thanks... THis is good stuff. How about timing? How do you disable the advance?

The advance is electronic.
When I set my timing I set it to the max advance at the specified RPM using an electronic timing light.
What I do is this. My max advance is 30 degrees at 3500 rpm. I then set my timing light to retard the timing flash by 30 degrees so at 3500 RPM it'll read "0" on the timing plate. Raise the RPM's to 3500 plus and set the timing mark to "0".
That's how I do mine.

On the 89 T-Bolt ignition you just set the timing at idle to the initial that you'll find on the valve cover or owner's manual. If you've got an advance timing light (or a timing tape on the balancer) you can set the total advance to 32-34 degrees at 3500.

Sorry, Iggy. We must have been typing at the same time. Patrick, do it the way Iggy says.

Prayers answered!
 

I have some good info to work with now. Thanks guys... Guess I better buy a new timing light!

Try this little test-take the air cleaner off and run the boat. Did the bog change at all? The secondary air door is controlled by a spring that is referenced to engine vacuum. This spring will fatigue over time and need to be reajusted. If I recall correctly, it's on top of the carb and looks like a small rocker arm. There is a allen screw that will allow you to adjust it. Which way to turn it and how much (or even if it's the right lever) I can't say.


Also check that filter at the carb inlet. Pay close attention to how it comes out and the exact position of the spring. You must put it back together the correct way.

If you're looking for a good timing light check out this one Digital Timing Light I have the same exact model. It's really easy to use.